Production of wood preservatives



July 28, 1942- J. E. HARVEY, JR 2,291,302

PRODUCTION 0F WOOD PRESERVATIVES Filed Aug. 14, 1940 wofmf/mr/wvcm/wm/ax/af @4740527 Patented July 28, 1942 PRODUCTION F WOOD TPRESERVAT-IVES .acquelin E. Harvey, Jr., Atlanta, Ga., assigner of'one-half toSouthern Wood Preserving Company, East lPointfG-a., acorporation of Georgia Application 'August 14, 1940,Serial No. 352,663

l2' Claims.

The present invention relates to Ithe tion of wood preservatives.

More spec11-"ically,'the present invention vrelates to the production ofwood preservatives of lowered 'corrosivity from tars of aromatic contentand fractions thereof.

An object of the present invention is 'the `induction of toxicity inhydrocarbons having little or no toxicity, and of increasing toxicity in-h-ydrocarbons having toxicity, whereby'to prov-ide, among other'things,woodpreserving oils -of lowered corrosivity, or materials havingVinduced toxicity and lowered corrosivity adapted to be added to theWoodpreserving oils or the like.

An object of the present invention is the --improving of toxic value inv/oodpreserving oils Yof current manufacture; the improving -of toxicproperties in the parent materials of woodpreserving distillates ofcurrent manufacture; vand the improving Aof toxic r,properties inresidual materials resulting from a distillation recovery 'of Woodpreserving voils from tars or the like; the improving of toxicproperties being yattended'gby lowering `of corrosivity.

Other objects of the present inventionwill be apparent from thefollowing disclosures.

The invention will be understood from the following description ofillustrative -steps cornprising various methods of securing the objectsof the invention, when read in connection with the accompanying drawingwherein the'igure is a diagrammatic sketch of 4an apparatus for carryingout a form of the process of the invention and wherein the nature of thestep carried'outineach chamber and the Acontentsthereof are indicated bylegend.

Example 1.--A sulphur bearing Vcoal tar :creosote of known toxic Valueand having la ispeciiic gravity of substantially 1.08,.a coke .residuevof in the order of 2% and substantially V135% 'residue above 355 C. istreated with hydrogen ata temperature of 350 C. and vapressure of ,300atmospheres; the thus treated coal tar creosote will be found uponinspection .toghave reduced corrosivity which advantage will passtothegnallyprocessed material. The coal tarcreosote vof reduced sulphurcontent is passed through a high pressure reaction chamber whilesimultaneouslyfilowing hydrogenv therewith, at a vtemperature :of 400 C.and ra pressure^of`200 atmospheres. The catalyst is molybdenum oxide,flow of hydrogen .111,000 cubic feet per barrel creosote and the timelof reaction 45 minutes. The beneficiated-creosote owing from thereactor `is inspectedffand found to have vincreased toxic properties asstemming producfrom among other things reduced coke-residue, `specific:gravity, and viscosity; vit will be found that there has' been inducednoY substantial-percentage of liquid vchain structures -or kindredmaterials that Yprecluded the induction cf-'toxicitm If anv unwantedpercentage Yof low boiling fractions -exist, they may be stripped tomake the newly formed oil of inducedtoxieity and lowered corrosivityconform in its 10W boiling end to-a wood ipreserving oil of tradeacceptance.

Example 2.-A sulphur bearing coal tan-specific gravity 1.1641 and cokeresidue of substantially above 10% is treated with "hydrogen atatemperature'of 325 C. and a pressure of 200 'atmospheres; the thustreated 'coal tar will be `found upon inspection to have reducedcorrosivity which reduction will be reflected in the nally processedmaterial. The coal tar of reduced sulphur content is .passed through ahigh .pressure reaction chamber while simultaneously flowing hydrogentherewith at a temperature of 395 C. and a pressure of 250 atmosphereswhile contacting a vanadium oxide catalyst. The flow of hydrogen is12,000 cubic lfeet per barrel feed stock and time of reaction one hour.

The beneciated coal tar flowing from the reactor is inspected-and foundvto have `increased toxic value vas stemming from among yother thingsreduced coke residue, specific gravity,\and -viscosity, and the Afactthat no substantial percentage oi liquid chain structures or kindredmaterials has been induced to lower toxicity, or make the inducedtoxicity of thepresent invention impossible.

In the event any percentage of undesirable low boiling fractions existinthebeneficiatedtarl said undesirable low boiling fractions may'bestripped to provide vconformance in the low boiling end to Woodpreservatives of trade acceptance. Thus, by the process of the presentinvention there is provided a -wood'preservingvoil of induced toxicityand loweredcorrosivity that conforms in-its low boiling end to a Woodpreserving voil of trade acceptance.

Example f3.-A sulphur bearing coal -tar fraction whose initial boilingpoint lis substantially 240 C. -and characterized `by content of highmolecular complexes is treated withhydrogen at a pressure of 200atmospheres 'and 340 C.; the thus treated coal tar fractionwill be foundupon inspection to have reduced -corrosivity which fact will inure tothe finally processed material. The coal tar fraction of reduced sulphur-content is subjected to the action -of a flow of hydrogen in thepresence of a molybdenum oxide catalyst while passing said tar fractionthrough a high pressure reaction chamber at a temperature of 400 C. anda pressure of 310 atmospheres. The flow of hydrogen is 15,000 cubic feetper barrel feed stock and the reaction period, "I5 minutes.

The beneciated coal tar fraction owing from -a reactor is inspectediandfound to have increased toxic value as stemming from amongv other thingsreduced coke residue, specific gravity, and vis-i .Shingle Stain Oil.

In the event any percentage of undesirable lowY boiling fractions existin the beneiiciated tar,

said undesirable low boiling fractions may be stripped to provideconformance in the low boiling ends to wood preservatives of tradeacceptance. Thus, by the process of the present invention there isprovided a wood preserving oil of induced toxicity and loweredcorrosivity that conforms in its low boiling end to a wood preservativeof trade acceptance.

If desired the beneciated tar or fraction thereof may be Ydistilled forthe recovery of a wood preserving distillate of enhanced toxic value;the distillation recovery may be eected to an upper limit so that thedistillate will conform in its low boiling end to a wood preserving oilof trade acceptance; or, the distillation may be effected to any desiredupper limit with the removal of, if necessary, low boiling fractions insaid distillate to provide spccication conformance.

In accordance with process of the present invention, wood preservingoils of varied characteristics may be made as for instance formingsubstitutes for any of the wood preserving oils noted in the following:

Woon PBEsnRvINe IMPREGNANTS Specification a. U b. U

a. Up to 210 C'., not more than 8% b. Up to 235 C., not more than 35% 5.A. W. P. A

p to 210 C., not more than 10% p to 235 C., not more than 40% 6. A. W.P. A.: Y

a. Up to 210 C., not more than 57 D Up to 235 C., not more than 15% 7`Prussian Ry.:

a. Up to 150 C., not more than 3% b. Up to 200 C., not more than 10% c.Up to 235 C., not more than 25% 3. N. P. V. & L. A. #220 a. 5% at 162 C.

b. 97% at 270 C. 9. S. P. S. S. O.:

a. 5% at 137 C.

b. 95% at 257 C. 10. N. S. S. O.:

' a. I. B. P., 150 C. b. 5% at 205 C. c. 95% at 292 C.

The abbreviations are explained as follows: A. W. P. A., American WoodPreservers Association; N. P. V. & L. A., National Paint, Varnish SzLacquer Association; S, P. S. lS. O., Southern Pine Shingle Stain Oil;and N. S. lS. O., Neville Catalysts of the present invention are oxides,as for instance oxides of metals of the 6th and 8th periodic groups; theoxides of other groups are usable, however, difiicultly reducible oxidesare preferred.

Concerning the reaction conditions in the step that lowers corrosivityby the action of hydrogen, temperatures and pressures may be chosenwithin a wide range inasmuch as sulphur reduction occurs at loweredtemperatures and pressures. The lower limit of Vtemperature and pressureis advisably that temperature and pressure which effects said reductionin a commercial manner, as regards the time element; pressures as highas practicable will operate, and the upper limit of temperatureadvisable is that temperature which causes under the conditions -of-theprocess no substantial deposition of carbon, as for instance coking. f

The step characterized by reduction of corrosivity may be carried on ina high pressure bomb or in a continuous manner in a reaction chamber orseveral reaction chambers, and in event of the continuous practice, thehydrogen flow is preferably maintained so as to induce no substantialcarbon deposit; as for instance coking. In the second cycle of hydrogenaction, flows of hydrogen in the order of {LOGO-15,000 cubic feet perbarrel feed have proven satisfactory, however, higher or lower flows,may be used, the high and low limits thereof being dened as those flowsthat induce undesirable coking.

By the term beneciated as used herein and in the appended claims ismeant the starting material at least once subjected to the action ofhydrogen in accordance with the present process.

Starting materials consist of tars of aromatic content and fractionsthereof characterized by sulphur content and capable of having toxicityinduced therein.

The present invention is predicated on, among other things, controllinghydrogen action in both cycles so that no substantial percentage ofliquid chain structures or kindred materials are induced that wouldpreclude or lower aforesaid toxicity induction. Hydrogen action is alsocontrolled so that no substantial percentage of the starting material isconverted to coke.

The second cycle of hydrogen actionV may be practiced at loweredpressures and temperatures; however, pressures of in the order of200-400 atmospheres are preferred, Vbut higher or lower pressures may beused. Temperatures in excess of 300 C. are preferred; however, lowertemperatures may be used, the upper limit of usable temperatures beingdefined by those temperatures that cause no inordinate coking action.

Some of the starting materials in which toxicity may be induced inaccordance with the present invention may contain high molecularcomplexes that are especially susceptible to thermal degradation; thesematerials may have toxicity induced therein while higher pressuresobtain with the added benefit that said molecular complexes are reducedto a greater extent, thereby enhancing toxicity induction.

The time element of the present invention in the second cycle ofhydrogen action is not circumscribed by any definite limit, but ismerely that period necessary to show toxicity induction; using somestarting feeds, periods of 30 minutes or less will result in theenhanced toxicity. Periods of one hour or longer may be used.

A In the first cycle ofY hydrogen action that re:

duces sulphur content, the reduction of sulphur may be accomplished inthe presence of a catalyst. Catalysts effective in the presence ofhydrogen are usable, as for instance the oxides and/or suldes ofmolybdenum, vanadium, uranium, cobalt, tin, manganese, tungsten, or thelike.

Starting materials previously subjected to the action of hydrogen aresuitable starting materials.

In the disclosures herein made the removing of low boiling fractions bygas movement or pressure release is considered the equivalent ofdistillation.

When reference is made to high molecular complexes contained in thestarting material, and When the starting material contains low boilingfractions that are not considered high molecular complexes, it is ofcourse obvious that the high molecular complexes contained in thestarting material are to a certain extent depolymerized by the solventpresent.

Starting materials of the present process also include sulphur bearingtars of aromatic content from which loW boiling fractions have beenremoved, as for instance tars from Which solvent oils have been removed.Viewed broadly, the starting materials of the present process aresulphur bearing tars of aromatic content, fractions of said tar moreviscous than the starting material due to removal of low boilingfractions from the starting material, high boiling fractions andpitches.

It will be seen that by reduction of sulphur content of the materialunder treatment during any stage of hydrogen action, the oxide catalystused during subsequent stages is at least partially protected from theeffect of the sulphur.

The term pitch as used herein includes the higher boiling fractions oftar, in other Words, tar from which low boiling ends have been stripped,such low boiling ends being suitable for use per se as creosote, otherWood preservative, or solvent. For instance, the final residue resultingfrom evaporating tar to dryness and then stripping wood preservativefrom the distillate is a very suitable pitch for use as a startingmaterial of the present process.

Minor changes may be made within the scope of the appended claimsWithout departing from the spirit of the invention.

I claim:

1. In the production of an oil of induced toxicity the process whichcomprises: subjecting a sulfur-bearing mixture of high temperature coaltar fractions to the sulfur reducing effect of hydrogen; thereaftersubjecting said sulfur-refined material to the action of a iiow ofhydrogen in the presence of an oxide catalyst at a temperature andpressure of at least about 300 C. and 200 atmospheres, respectively;carrying on the process for such a length of time as to provide an oilof the Wood preserving type having induced toxicity conforming inboiling points according to specifications accepted in the trade for atar-derived wood preserving impregnant.

2. In the production of an oil of induced toxicity the process Whichcomprises: subjecting a sulfur-bearing mixture of high temperature coaltar fractions to the sulfur reducing effect of a flow of hydrogen at atemperature not substantially less than 325 C.; thereafter subjectingsaid sulfur-refined material to the action of a flow of hydrogen in thepresence of an oxide catalyst With time, temperature and pressure socontrolled as to provide an oilof the Wood preserving type havinginduced toxicity and conforming in boiling points according tospecications accepted in the trade for a tar-derived wood preservingimpregnant.

JACQUELIN E. HARVEY, JR`

